The present invention relates to an apparatus for cleaning both sides of substrates, such as LCD substrates or semiconductor wafers.
In a process for manufacturing semiconductor devices, both sides of semiconductor wafers must be cleaned. Therefore, contamination, such as particles, organic contaminants and metal impurity, allowed to adhere to the both sides of the wafers must be removed. To remove contamination from the both sides of the semiconductor wafers, a single wafer type apparatus for cleaning both sides of semiconductor wafers has been employed with which semiconductor wafers are sequentially processed.
As the apparatus for cleaning both surfaces of semiconductor wafer, there are apparatuses of two types, i.e., a reversing type wherein the front-side and the back-side surfaces of wafer are cleaned independently, and a non-reversing type wherein both-side surfaces are cleaned simultaneously.
Since the apparatus of the reversing type (the former) is provided with a reversing unit for reversing the wafer W in addition to the cleaning unit, it becomes large-sized and has low throughput.
As shown in FIG. 1, a conventional apparatus 100 for cleaning both sides of wafers incorporates a cup 108 disposed in a case 109, a spin chuck 101, a motor 102, a back-side cleaning mechanism 106 and a front-side cleaning mechanism (not shown). The spin chuck 101 is connected to a rotational drive shaft 103 of the motor 102, the spin chuck 101 incorporating four support arms 104 radially extending from the center of rotation of the spin chuck 101 and holding members 105. Each of the holding members 105 is joined to the leading end of each of the support arms 104. The foregoing holding members 105 are brought into contact with an outer end of a wafer W so as to horizontally hold the wafer W. The back-side cleaning mechanism 106 is disposed below the spin chuck 101. The back-side cleaning mechanism 106 has a nozzle 107 for discharging and supplying process liquid to the back side of the wafer W.
As shown in FIG. 2, the nozzle 107 supplies the process liquid to the back side of the wafer W through a space 110 between the support arms 104 of the spin chuck 101. However, a gas-liquid interface is undesirably generated on the back side of the wafer W on which the supply of the process liquid to the same is obstructed by the support arms 104. Thus, the back side of the wafer W cannot sufficiently be rinsed. What is worse, foreign matter, such as particles, can easily be allowed to adhere to the portion in the vicinity of the gas-liquid interface. Thus, there is apprehension that the back side of the wafer W is contaminated. Moreover, the rotating support arms 104 reject the process liquid, thus causing a great quantity of the process liquid to be consumed wastefully. Thus, the running cost is enlarged excessively.
As a conventional apparatus of another type, an apparatus 120 for rinsing two sides of wafers is known, the apparatus 120 incorporating a nozzle 126 structured as shown in FIG. 3. A rotational table 124 arranged to be rotated by a rotating mechanism 130 is disposed in a cup 121 of the apparatus 120. A nozzle 126 is disposed to face a central portion of the back side of a wafer W held by the rotational table 124. The rotating mechanism 130 is provided with a motor 134, a driving pulley 133, an idle pulley, a belt 132, and a rotating shaft 123. The rotational driving force of the motor 134 is transmitted to the rotating shaft 123 through the belt 132. A supply pipe 125 of the nozzle 126 passes through a rotating shaft 123, and then the supply pipe 125 is allowed to communicate with a process liquid supply unit (not shown).
The process liquid splattered from the rotating wafer W generates a great quantity of splashes of the process liquid in the cup 121. On the other hand, particles are generated in the rotating mechanism 130. To prevent contamination of the wafer W, the communication between the processing atmosphere in the cup 121 and the atmosphere in the rotating mechanism 130 must be prevented.
However, a small gap 127 exists between the rotating shaft 123 and the cup 121. Therefore, fine dust generated in the rotating mechanism 130 is introduced from the rotating mechanism 130 into the cup 121 through the gap 127. Thus, the introduced dust is allowed to adhere to the back side of the wafer W. Splashes of the process liquid is introduced into the rotating mechanism 130 from the cup 121 through the small gap 127. Thus, the rotating mechanism 130 is contaminated. Since a small gap 128 exists in a portion in which the nozzle 126 projects over the rotational table 124, the process liquid is introduced into the supply pipe 125 through the gap 128. Thus, the rotating mechanism 122 disposed below the supply pipe 125 is contaminated. As a result, the rotating mechanism 130 easily produces trouble.